to straight pipe or not to straight pipe that is the question

[mazdarotary]

Hello again all,



When I bought my truck a few years back the PO had the exhaust system modified to exit before the rear tire due to the kelderman suspension system in the rear and the transfer flow tank mounting where the spare used to sit. The exhaust is the stock down pipe then bumps up to 4 inch into a big pill shaped resonator and then turns out in front of the tire. Well a few weeks back the tail pipe hanger broke and it put some stress on a welded fitting from where it changes sizes in front of the resonator. I fixed the hanger but just the other day the weld in front of the resonator let go so now I have really only the downpipe and maybe some of the exhaust going through the resonator and tailpipe. It has gotten a bit louder but not that bad really. It was always pretty loud before. Sorta sounded like a big rig. I notice the turbo noise a bit more now with the extra short exhaust. My question is. I have a stock muffler from a 2001 cummins that the PO had pulled off of his motor home and sent with me with the truck. I have a appointment with a exhaust shop for saturday and was wondering if i should just go straight 3" from the turbo back to the same in front of tire location as before?Or should I use the muffler?The shop doesn't do 4"tube but that doesn't really matter much to me anyway because the downpipe is only 3" anyway. Do you guys think the straight pipe would be too loud?Or any louder than it is now with the broken exhaust?Sorry to be so long winded. Thanks in advance.





Chris

92 D250 CC

74 Mazda rotary truck

83 Mazda RX-7 limited edition

 

[tURBOdIEZEl]

i say straight pipe it! ofcourse thats coming from someone who loves the sound of a kw... ... i threw an aftermarket exhaust on my truck and kicked the kat to the curb which made a noticable difference! you'll expirence lower egt's and a quicker throttle response not to mention you will be able to hear that turbo spool up... ...

 

[tugboatphil]

Chris,



I can only imagine that up in the Northeast, they probably have vehicle noise laws. Now if you have a muffler in the system (whether or not anything is left inside) they can't as easily give you a ticket. However, if Smokey looks underneath and doesn't see one at all..... tell it to the Judge.



I swapped tailpipe and mufflers from my 90 to the 93. Since I live in the country, I decided to see what she sounded like. I wish I could run it that way all the time. It wasn't that much louder (well... . maybe it was) but I make several trips a month to the state capitol for work. Cops down there LOVE giving tickets to noisy, smokey trucks.



It's straight pipes on the big trucks which cause lots of small towns (especially in Ohio, sorry Scott!) to enforce "No Jake Brake" laws within their town limits. A Jake by itself is not that noisy, and it's a great safety device. But magnify the sound, especially in towns that get lots of truck traffic, and they'll be gunning for you.



To sum it up, do what you want to. For every action, there's an equal and opposite reaction.

 

[mazdarotary]

Thanks for the replies guys. I guess my other question is. Will the factory 01 diesel muffler kill any performance?Will it choke the engine down,and raise EGT's?



Chris

 

[tugboatphil]

As I was hinting at, in the old days, we used to pull packing out of mufflers, so they'd look like the real deal. I don't know exactly what's in these big things. But if you can get it out with a hooked metal rod, there goes your back pressure and it still looks like a new muffler.

 

[sparks57]

Dude, just loose the muffler, you won't look back...

 

[dpuckett]

Stick with the 4". I have it on mine, and it made a real noticeable difference in spoolup, even though my downpipe is half 3" and I have the adaptor on top of a 4" elbow. Looks crappy, but that matches the rest of it, so it fits right in, so to speak.



Try going to a KW, Peterbilt or Freightliner dealer and see if they have 4" parts- elbows, straight pipe, etc. You can make one yourself for well under $100. If you have a stick welder, use a 3/32 6013 @ about 80-90 amps- it isnt as hot as a 6011 or 6010, but will stil get it all together.



Daniel

 

[phillips5]

Never had a muffler on any of mine or my brothers cummins pickups. I live and breath in ohio nobody has given me a ticket yet.

 

[Greenleaf]

Loose it. Keep the 4".



A Turbocharged Diesel is much MUCH quieter than a V8 gasser with two cherry bomb "mufflers" You will not have a problem. Read that "hassled" by the law, unless you do something deliberate, ie make lots-o-smoke while a officer looks on. Then u are simply drawing attention to yourself.



I have sat next to a police cruiser and diddn't get any looks. I mind my own and do not draw attention (advertise) the fact.



Them Harley Davidson bikes run all over town up one side and down the other with no mufflers and they do all they can to make noise. Don't see anyone hassle'n them. And they LOOK like trouble.



I have a four inch straight pipe terminating at the front of the right rear tire (the last I checked) Has anyone SEEN my truck? getting worried now.



Scott

 

[JLEONARD]

I have the 4 inch WITH a muffler, for the exact reason Tugboat was talking about... .

When I switched from the stock to the 4 inch system, I saw a big performance improvement.

The muffler also keeps the drone down on long trips.

I would try the muffler first as is... then remove it and torch out the guts if you want... ... .

That way you will appear "legal" to a cop... . and the emissions inspectors if that applies in "taxachussetts".

Jay

 

[DieselBuzz]

To pipe or not to pipe?

In Mass. to pass inspection you are supposed to have a muffler. I got inspected and passed twice without one. In Jan. the state trooper at my job told my head mechanic that if I didn't get one he would ticket me. I got the muffler. I miss the sound of the straight pipe. I don't know anyone with a torch to cut the center out of my muffler, this would be my choice. Good luck with what ever you choose.



PS I don't believe there are any emission requirements for inspection in MA.

 

[Greenleaf]

I should ask my bus inspector the same. Use a fictitious name of 'corse



Say something 'bout..... "this friend of mine has this diesel truck and the exhaust has rotted out/away". "He has no $$$ and would like to run only pipe". "Is it leagal to only have the turbo to silence the exhaust"? "He wants to stay within the bounds of the law, you see".



Greenleaf

 

[Greenleaf]

OK guys, just spoke to/with my local State Trooper post... .....



They don't know



Scott

 

[Forrest Nearing]

I looked on the TX DPS website, and a turbo is considered a muffler... check your local laws and print them out to show any officer who may have a question. or you could just go with a dummy muffler and never worry about it.



Forrest

 

[Mel Fuelling]

DieselBuzz,

If your muffler is not rotted out, remove tailpipe, then muffler with a come-a-long pulled tight, then apply torch heat to the wrinkled area where the muffler clamp was. Apply tension, heat, apply tension, heat until it slips off without damage. Cut muffler open on bandsaw (or with sawzall or hacksaw), remove all internal organs, gas weld (my choice) or mig muffler back together, paint

and reinstall. Looks stock. Quicker to do than to write.



Mel

 

[Flexiheep]

joined the club

Well, I jumped in and joined the high clearance exhaust club. Oo. Oo. I bought a 42" section of pipe, a couple clamps and and had it swagged for 20 bucks and threw it on after work today. I'll weld up the mounts tomorrow morning when I am working on the new bumper for the front (using a coat hanger right now of course).

Impressions are that it is quieter in the cab than I expected, also a lower tone. under light throttle I still pretty much only hear the music from under the hood, though the carpet is out currently too so it is louder inside than normal. Under heavy throttle it isn't bad at all though you definitly hear it bouncing off parked cars, kinda blatty if that is a real word. I can't say anything about EGTs or real numbers since being stock I haven't put gauges in yet. Also still using that highly restrictive stock tail pipe and a loose auto.



Hope this helps someone thinking about jumping in.

 

[bflood]

Straight Pipe

I went for the straight pipe with my 3" system. Sounds great but not really that loud. The turbo breaks up the flow and keeps the noise level reasonable (not like a gasser at all). I don't have any measurements but I'm confident it lowered EGT's some. I haul heavy so that is important to me.



Gutting the muffler would work nice but its more work . . . up to you. If you could also keep the 4" tail I'd think that would help too.



In CT my truck, being rated over 10,000#, is exempt from emmissions so, unless I got stopped, I don't worry about an inspection discovery. I use throttle descretion when prudent (like going past "authorities".



Good Luck,

Bruce

 

[EZGZ]

I ran a straight pipe in front of pass wheel for a year or so. Then decided to go with the full Banks set up.



Me likey Banks!

 

[tURBOdIEZEl]

just straight piped the rig tonight with some 5" stacks. sounds awesome! ill post pics as soon as i can (its supposed to rain here the next couple days. )

 

[TKingsbury]

So, did you get your exhaust done mazdarotary? My . 02 may be late, but here goes. If you are required to have a muffler, why not run a straight through style with a smooth bore? If you are not required to have one, don't. My truck has a piece of tube where the muff used to be. It's the stock exhaust otherwise. It's not too loud although my neighbor told me he hears me leave for work in the morning. I like the sound and it's good inside the cab at any throttle position.

Travis. .